1. Field of Invention
The present invention relates to a method of determining a diesel oxidation catalyst (DOC) regeneration cycle of a vehicle, which can activate DOC and can improve the purification performance of DOC.
2. Description of Related Art
When a diesel engine is running, exhaust gas is discharged from the diesel engine. Exhaust gas includes HC, CO, soluble organic fraction (SOF), soot, particulate matter (PM), and the like. When the materials included in exhaust gas are directly discharged into the air, serious environmental problems, such as air pollution and the like, occur. Therefore, these materials must be suitably purified before being discharged. For this purpose, a diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC) of a vehicle are used. A DPF collects PM in the air, and then periodically burns and remove PM after a predetermined amount of PM has been collected. A DOC is a dual catalyst that converts CO and HC into CO2 and H2O by oxidation, and removes SOF from exhaust gas, and then discharges the purified exhaust gas into the air.
Meanwhile, the EURO-6 “automobile exhaust gas regulation” will be applied from 2014. The average exhaust gas temperature must be controlled to 140° C. or less according to EURO-6, and thus the exhaust gas discharged from a diesel engine must conform with EURO-6. Further, the exhaust gas temperature based on EURO-6 becomes lower than the exhaust gas temperature based on EURO-5, and thus the activity of a catalyst must be improved such that the catalyst efficiently operates even at low temperature. In this case, in order to improve the activity of a catalyst at low temperature, the amount of a precious metal in the catalyst must be increased. However, when the amount of a precious metal in the catalyst increases, the catalyst becomes expensive, and the activity of the catalyst at low temperature does not greatly increase even when the amount of a precious metal is increased, so that it is required that the activity of the catalyst be improved using other methods.
A diesel engine generally operates in a lean fuel-air mixture state. However, when a rich fuel-air mixture is periodically supplied, the DOC activity increases. When the cycle of supplying a rich fuel-air mixture is excessively short, the fuel efficiency of the diesel engine becomes low. Further, when the cycle thereof is excessively long, the diesel engine is advantageous in terms of fuel efficiency, but contaminants are not effectively removed compared to when a conventional catalyst is used, because the rich fuel-air mixture returns to the state of a rich fuel-air mixture not being supplied. Therefore, in order to effectively improve the DOC activity, a rich fuel-air mixture must be resupplied when the effect of improvement of the DOC activity attributable to the previously-supplied fuel-air mixture remains to some degree.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.